(a) Technical Field
The present invention relates to a key update method based on the amount of communication in wireless sensor networks having a hierarchy structure.
(b) Background Art
A wireless sensor network is configured to include a large number of sensors, wherein each sensor senses a predetermined area and information sensed by the sensors is transmitted to manager nodes managing all the information through a predetermined path. In this case, the hierarchy is formed between the nodes to transmit the information to the manager nodes. As described above, the related art for efficiently managing keys in the wireless sensor network having the hierarchy structure generally uses key pre-distributing methods using keys put in the nodes prior to distributing the nodes.
An example of the key pre-distributing methods may include a key management method based on key pre-distribution. In the method, each node has keys corresponding to predetermined numbers prior to being distributed. After the nodes are distributed, each node uses commonly distributed keys to generate keys that can communicate with adjacent nodes. When the commonly distributed keys are not present between any two nodes, theses nodes use commonly distributed keys of adjacent nodes to generate keys that can indirectly communicate with the adjacent nodes.
However, the method may cause any problems when the sensor are captured by an attacker, because the number of commonly distributed keys is set to be one so that the commonly distributed key may not be used for communication. In order to solve the problems, a method for generating keys to be used for communication only when the commonly distributed keys are q (>1) or more has been proposed.
Meanwhile, it can be appreciated that another key pre-distributing method may reduce the number of available pre-distributed keys when a key pre-distributing server knows an area in which nodes are distributed. According to the method, the key pre-distributing server divides the area in which the nodes are distributed into several small areas and distributing some keys to key pools in each area, such that the small areas may share more common keys. As a result, even though the number of pre-distributed keys to be used by the nodes is reduced, two adjacent nodes may easily search the common keys.
Meanwhile, as yet another key pre-distributing method, a key pre-distributing method using sensors distributed in a group has been proposed. Since the sensors belonging to the same group are closely disposed to one another, the possibility that the keys distributed to each node by the key pre-distributing server are common keys to one another has increased. When the adjacent nodes belong to other groups, the nodes serve as an inter-group gateway so as to help forming path keys between the nodes belonging to several other groups.
In the wireless sensor network having the hierarchy structure, a need exists for a new method for effectively managing keys to be used by the sensors. The wireless sensor network for the hierarchy structure participates in communication by generating symmetrical keys for security. In this case, the wireless sensor network having the hierarchy structure can obtain information regarding the used symmetrical keys when the nodes are captured by attackers, thereby causing problems in network security. In addition, when communication with the nodes at which a large amount of communication is present is performed, the exposure of keys may be increased due to frequent communication. Therefore, a need exists for a method for effectively updating keys.